Get the rolling pins and cake tins out of the cupboard: today is Pi Day! From Limburgse vlaai to a steaming apple pie on a windowsill, today is all about baking. But not just physical baked goods are in the spotlight. The brains of the most talented scientists are also important today. A real pie is usually round. Circular shapes and mathematics. A lowercase Greek letter. 3.14…and what was it again? Even if you don't want to know the exact circumference of your cake, enjoy pi today — even after the decimal point.